Semi-finished products and components for motor vehicles need to meet different requirements depending on the location in which they are used within the motor vehicle and the purpose for which they are used. The forming properties of the aluminium alloy or the strips and sheets are of decisive importance during the manufacture of the semi-finished products and components for motor vehicles. The strength properties, but also in particular the corrosion-resistance properties play an important role during the later use in the motor vehicle.
For example, in the case of structural components of a motor vehicle, for example interior door parts, the mechanical properties are primarily determined through their rigidity, which depends above all on the shape of the interior door parts. In contrast, tensile strength for example has more of a secondary influence. However, the materials used for an interior door part may not be too soft. In contrast, good formability is particularly important for the introduction of aluminium alloy materials in motor vehicle applications, since the components and semi-finished products undergo particularly complex forming processes during manufacture. This applies in particular to components which are manufactured in a single piece as a formed sheet metal shell, for example sheet metal interior door parts with integrated window frame region. By dispensing with joining operations, such components offer significant cost advantages in comparison with, for example, a joined aluminium profile solution for the window frame. The aim is for example to be able to manufacture semi-finished products or components in a single piece of an aluminium alloy, using as few forming operations as possible. This requires an optimization of the forming behaviours of the aluminium alloy which is used. The aluminium alloy of the type AA5005 (AlMg1) occasionally used for similar applications does not fulfill these requirements, since it does not possess sufficient forming capacity due to hardening which takes place during forming.
A further important role is played by corrosion resistance, since components of motor vehicles are frequently exposed to perspiration, condensation and sprayed water. The aluminium alloy which is used must therefore be as corrosion-resistant as possible, in particular resistant to intercrystalline corrosion and filiform corrosion in the painted state. Filiform corrosion is understood to mean a corrosion type which occurs in coated components and which displays a filamentary pattern. Filiform corrosion occurs at high atmospheric humidity in the presence of chloride ions. Although the aluminium alloy of the type AA8006 (AlFe1.5Mn 0.5) exhibits sufficient strength and very high formability, it is susceptible to filiform corrosion. The alloy AA8006 is therefore less suitable for coated, in particular painted components such as interior door parts.
An aluminium alloy is known from the applicant's as yet unpublished patent application PCT/EP2014/053323, as an alternative to the aluminium alloy of the type AA8006, which contains the following alloy components in % by weight:    Fe≤0.8%,    Si≤0.5%,    0.9%≤Mn≤1.5%,    Mg≤0.25%,    Cu≤0.20%,    Cr≤0.05%,    Ti≤0.05%,    V≤0.05%,    Zr≤0.05%,the remainder aluminium, unavoidable accompanying elements individually ≤0.05%, in total ≤0.15%, whereby the total of the Mg and Cu contents fulfils the following relationship:0.15%≤Mg+Cu≤0.25%.
It has been found that also this aluminium alloy offers scope for improvement, in particular with respect to its forming behaviour. Moreover, the high Mn content leads to problems in recycling this aluminium alloy when it is mixed, in the scrap cycle, with the Al—Mg—Si alloys of the alloy type AA6XXX usually used in automobile applications.
Starting out from this prior art, the present invention is therefore based on the problem of providing an aluminium alloy for the manufacture of semi-finished products or components for motor vehicles which is highly formable, of medium strength and highly corrosion-resistant. In addition, a method for the manufacture of a strip made of a corresponding aluminium alloy, an aluminium strip or sheet, its use and a structural component of a motor vehicle are suggested.